The custom profile fields are made to ask your member to add some additional information like the Steam ID, ESEA name and stuff like that. The custom profile field(s) are also shown in the user-exports.
Name - Just write in the title of the field here.
TEXT INPUT - can be used for a short text like League IDs or names.
TEXT AREA - can be used for a larger text like 'about me'.
DATE - can be used for a join date or birthday